This project is designed as a comprehensive interdisciplinary approach to the problem of generalized vasculitis in man. The assumption is that immunologic mechanisms are of primary importance in the etiology and pathogenesis of vasculitis. Analysis of immunologic components will be made by studying patients with regard to; a) their history of exposure to agents known to induce allergic vasculitis, b) their general immunologic reactivity, c) morphologic analysis of lesions by conventional histology, immunofluorescence microscopy and ultrastructure using horse radish peroxidase methods, d) analysis of complement mechanisms, e) cryoproteins, f) hepatitis B antigen, g) lymphocyte physiology. Well-studied examples of vasculitis, e.g. SLE, will not be included.